The normally crystalline vinylidene chloride polymers are widely used as barrier and heat seal coatings for paper, films and sheets. For optimum properties, such coatings are generally deposited as a film forming aqueous dispersion of latex. Heretofore, such coatings have been formulated with significant amounts of natural or synthetic materials such as the ester waxes, talc, clay or calcium carbonate to prevent undesirable agglutination, i.e., blocking or sticking of wound-up films and the like coated articles, particularly when such latexes are used to coat polyolefin film and especially corona or flame treated polypropylene film (as discussed in U.S. Pat. No. 3,387,997).
The prior-used formulation additives have generally been found to be effective for minimizing blocking of coated film structures, however, their presence in the coating material results in an undesirable reduction in the oxygen barrier properties of such coatings.
It is the primary object of the present invention to provide a means for obtaining heat-sealable coatings based on the normally crystalline vinylidene chloride polymers which coatings have enhanced resistance to blocking without significant detriment to oxygen barrier properties. It is a further object of the invention to provide highly useful composite articles utilizing such coatings.